Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?

Posted: Fri Nov 30, 2012 5:08 am

Medium Poster

Joined: Tue Jul 14, 2009 2:40 amPosts: 98

BWD wrote:

The kiter himself is the greatest limit at this point!The human body turned sideways is not as aerodynamic as a fuselage.The control system requires dealing with heeling forces etc. using the body to control board and kite.The lines are more of a problem the faster you go, and so on...Once they get to v3 sailrocket, they may see 80+ knots.It's very hard to get there!But kiters can go faster than the current 55.65kts, and will...How to improve design for this?Everybody has ideas...

Agreed, scale the kite up, and harness the kite directly to the board with larger fins.. remove the human limitation of having to hold the kite down... Nobody is holding down the sail on the sailrocket.. there's some guy maneuvering a joystick or something. I was under the impression that this competition was with regular commonly used vehicles..

Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?

Posted: Fri Nov 30, 2012 5:51 am

Very Frequent Poster

Joined: Sun Sep 04, 2011 5:37 pmPosts: 1855

plummet wrote:

First up get a dude legless dude and create some foils for his legs so they create aparent wind and go super fast.... sorta like the cheeta legs of kite surfing.

I'm gonna DO that !!Dump the feet off my prosthetics ; plug the straight into the foil with carbon airfoil.Won't be needing the surfboard for flotation on that one ; At Mohave, i gotta use alife jacket anyway, it's a law.

I don't think kites are the limiting factor yet. Once boards improve, then kites will definitely need to improve. But that should not be too difficult. We could make them like paraskiflex or C-quads, but with racing profile. The kite will hindenburg uncontrollably if it is truly low drag, but we can add a small fifth line to distort the profile and add drag to allow flying at low speeds until we are cruising. Then pull or release the fifth line and the kite becomes super efficient.

What good is there to try and chase a silly speed record? Well we don't get a awesome new system for everyday use, but certain parts of the system provide innovations for everyday use. Sail rocket just proved that a fin could work up to 65 knots (whereas most literature shows that above 50 knots a water foil efficiency becomes useless).

And chasing a record is simply a nice challenge that keeps one thinking and innovating. With Sail Rocket's speed now it has become more of a theoretical challenge than a physical one, until we find some major break through.

Dave you are right. I do not know why I have 50 knots in my head? Maybe where most of the problems lie most of the time and I made wrong assumption?

But faster foils like propellers and higher speed motorized hydrofoils make use of supercavitating foils don't they? I do not think sail rocket had such a design, otherwise the fence they added would not make sense, but I must admit I do not know much about their system.

This design is still currently the world’s fastest hydrofoil having exceeded 130 MPH in 1976. His developmental progress has been published in industry journals and periodicals worldwide and Ken is considered the world’s foremost authority on supercavitating hydrofoil design.

So supercavitating foils can go very fast (130mp=112knots). But I do not know how efficient they are and whether that could work.

Do you know what is the limiting factor holding back a course race boards from going over 50 knots? Maybe it is the kites and not the large fins? I am sure it is the fins starting to cavitate?

We need better kites. Right now we have an enormous tube, which limits our upwind performance. So the kiter has to have massive strength like Rob Douglas in order to resist the downwind pull.

With a more efficient kite, you don't need as much strength resisting the kite's drag and kiters could do another 30 knots. Cabrinha designed these kites for going 20-30 knots, not 60-70.

Like the initial post said, we have to go back to the drawing board, and it's going to require a big R&D effort by Cabrinha or maybe Ozone, they might be interested too, lots of money and time thrown into a one of a kind kite.

I think our boards are ok, because that is the one part where kiters are able to tinker easily with the board, tweak it, build it up, build it down, change shape, for very low cost, so I think our boards already have a lot of R&D put into them from kiters doing trial and error until they got it right.

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